In modern times with progressive and developing technologies, liquid crystal displays (LCDs) have been extensively applied to electronic display products such as TV, computer displays, notebook computers, mobile phones, or personal digital assistants (PDAs). An LCD includes data drivers, scan drivers, and an LCD panel. An LCD panel comprises a pixel array. The scan drivers are used for turning on multiple pixel rows in the pixel array sequentially for scanning pixel data output by the data drivers to pixels and thus displaying images.
A general decoding and scan driver comprises a decoding circuit, a plurality of level-shift circuits, and drivers. The decoding circuit outputs a decoding signal to the plurality of level-shift circuits and the drivers according to a decoding control signal. Then the plurality of level-shift circuits and the drivers generate scan signals sequentially according to the decoding signal for scanning the display panel. The LCD panel uses the gate to turn on the internal cells and uses the source to transmit accurate voltages for controlling the orientation of the liquid crystals in the display panel. Because the output voltages of the gate are the high power-supply voltage (VGH) and the low reference voltage (VGL), high voltage devices should be adopted. The level-shift circuits and the drivers need to raise the scan signal to VGH and VGL, leading to increase of areas.
Nonetheless, because a general decoding and scan driver decodes at the low-voltage stage first and then drives the drivers via the plurality of level-shift circuits, each driver needs to have the level-shift circuit for shifting the level of the control signal, which means at least 10 high-voltage transistors and two resistors for forming a scan driver. Consequently, according to the prior art, the area, and thus the cost, of the scan driver are increased.
Moreover, because there are various types of scan drivers for LCD panels, for example, different sizes of LCD panels or different driving methods, the voltage of the driving signals generated by the scan drivers are different. However, according to the type of LCD panel, when the scan driver only needs to generate low-voltage driving signals, such as shifting from 1.8V to 5V or from 1.8V to −5V, if the decoding and scan driver adopts the level-shift circuit, the circuit area of the decoding and scan driver increases, resulting in increase in cost.
Accordingly, the present invention provides a novel decoding and scan driver for saving the area as well as the cost.